1. Field of the Invention
The present invention relates to the dechlorination of highly chlorinated methanes, characteristically chloroform (CHCl.sub.3) and carbon tetrachloride (CCl.sub.4).
2. Description of the Prior Art
The syntheses of chloromethanes on an industrial scale are based on the chlorination of methane or of methyl chloride (CH.sub.3 Cl) and, as this reaction is simple, they are not completely selective. For example, it is not known in this art to produce methylene chloride (CH.sub.2 Cl.sub.2) without concomitantly producing chloroform and carbon tetrachloride.
The chloromethanes are valuable intermediates and if, for example, only chloroform is required for a particular synthesis, the presence of the accompanying carbon tetrachloride becomes problematical. Need thus exists in this art for processes for the dechlorination of a chloromethane to convert same into a less highly chlorinated compound, or even into methane.
U.S. Pat. No. 3,579,596 describes reacting carbon tetrachloride or chloroform in the gas phase with hydrogen on a platinum catalyst. According to this '596 patent, the carbon tetrachloride is degraded to chloroform and methane. During such process, however, fouling of the catalyst and an instability of the reaction temperature are observed.
A similar reaction is described by Alvin H. Weiss, Baljit Singh Gambhir and Richard B. Leon in "Hydrodechlorination of carbon tetrachloride", Journal of Catalysis, 22, pages 245-254 (1971).